The focus of this pilot study is to collect samples from twenty families who have two or more members with autism or related disorders. This project will perform a full genome search and genotype each individual to localize susceptibility genes for autism. Applied Biosystems GeneLink primers will be the system used. The fluorescence-labeled primers are used to amplify marker alleles from the genomic DNA of probands and family memebers. These markers are designed for linkage analysis, thus, virtually all informative meioses can be utilized. The data collected through genotyping will be examined using affected sibpair and affected pedigree member linkage analyses to determine potential candidate loci for autistic disorders.